How can I keep/get rid of the algae growing on the filter in my filter tank?

I have a 10 gallon fish tank which used to stay fairly clean on its own. Sure, I got some algae on the gl and plants and hard algae on the rocks, but that was about it. I have a plecostomus in the tank with driftwood, but he never seems to clean the walls of the tank anymore. So, I got a Chinese Algae Eater. He cleans some, but not much. Anyway, the last couple months, my filter cartridges have started needing replacing every week instead of every month and the past month the filter (where the water pours out) has gone from growing a brown algae at a slow rate to a blue-green algae very quickly, to the point where it hangs off the edge and almost ds into the water. Nothing has changed except I have one fewer fish. The tank gets light from the tank light and kitchen light, but doesn't get any direct sunlight. Any ideas as to how to prevent this and how to get rid of it for good?